Case IH 3697 – Engine Control Unit (ECU): Failure in glow plug cylinder 3

The engine control system has detected an electrical fault—such as an open circuit, high resistance, or a short—specifically on the glow plug heating element for the engine's third cylinder.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Farmall
• Maxxum
• Puma

1. 1

   Visual Inspection: Inspect the wiring harness, connectors, and the electrical bus bar leading to the cylinder 3 glow plug. Look for signs of corrosion, melting, or a loose connection.

2. 2

   Resistance Test: Disconnect the battery and remove the bus bar from the glow plugs. Use a digital multimeter to measure the resistance of the cylinder 3 glow plug by placing one probe on the plug's terminal and the other on a clean engine ground. A healthy glow plug typically reads very low resistance (e.g., 0.3 to 0.8 ohms). An infinite reading (open circuit) confirms the internal heating element has failed and the plug must be replaced.

3. 3

   Voltage Test: Verify that voltage is actually reaching the glow plug bus bar when the ignition key is turned to the "ON" position during the cold-start pre-heat cycle.

4. 4

   Control Unit Check: If the plug tests fine but the code persists, the issue may lie in the glow plug control unit/relay or a break in the wiring harness between the ECU and the engine block.

1. 1

   Safety First

   Turn the machine's battery disconnect switch to the OFF position to prevent electrical shorts.

2. 2

   Access the Plugs

   Locate the glow plugs on the engine cylinder head. You may need to unbolt and relocate interfering hose assemblies or brackets to get a straight angle on cylinder 3.

3. 3

   Remove Wiring

   Remove the retaining nut that secures the electrical bus bar to the top of the glow plugs. Carefully lift the bus bar away.

4. 4

   Prep for Removal

   Apply a high-quality penetrating oil to the base of the glow plug and let it soak (doing this while the engine is slightly warm can help).

5. 5

   Remove the Glow Plug

   Using a deep socket and a torque wrench, carefully unscrew the glow plug. Do not force it. Exceeding the shear torque limit will cause the plug to snap off in the cylinder head, resulting in a massive repair bill.

6. 6

   Clean the Port

   Ensure no dirt or metal chips fall into the open cylinder. Clean the glow plug port and electrical contact points.

7. 7

   Install the New Plug

   Insert the new glow plug (ensure any required sealing rings are in place). Thread it in by hand to prevent cross-threading, then tighten to the manufacturer's specified torque (typically around 8 to 10 Nm for standard M8 glow plugs).

8. 8

   Reassemble

   Reattach the electrical bus bar and tighten the retaining nuts securely.

9. 9

   Test and Clear

   Turn the battery disconnect switch back ON. Cycle the ignition to verify the glow plug pre-heat operates correctly. Use a CNH Electronic Service Tool (EST) or compatible diagnostic scanner to clear the 3697 fault code from the Engine ECU.